1. Field of the Invention
The present invention relates to an apparatus and a method for recreating radio frequency (RF) field conditions using previously collected data, thus allowing wireless communications equipment testing and optimization without repeated field testing.
2. Description of Prior Art
The complexity of a typical cellular communication network, particularly a code division multiple access (CDMA) network, makes it difficult to accurately analyze, test, and optimize network parameters and equipment using computer simulation. Thus, field testing is typically performed using a mobile diagnostic device connected to a mobile phone (xe2x80x9cmobilexe2x80x9d) to gather field test data as the mobile moves throughout the network region.
One known mobile diagnostic device collects CDMA field data representing carrier and interference levels seen by a mobile, and stores the collected field data as a field test data file.
A mobile in a CDMA network repeatedly searches for and detects pilot signals transmitted from network cell sectors. The relative strengths of the pilot signals allow the mobile to determine which cell sector should handle call traffic, and allow controlled handoffs between cell sectors as the mobile moves through the CDMA network area. The mobile diagnostic device collects xe2x80x9csearcherxe2x80x9d data for each pilot detected by the diagnostic mobile at frequent intervals. Specifically, the mobile diagnostic device collects an Ec/Io value, representing the ratio of energy measured at the mobile""s demodulator to overall interference, for each detected pilot. The mobile diagnostic device further measures total pilot signal power, Ptpilot, received at the mobile at time t.
To optimize system parameters of a deployed cellular network, and test new algorithms (e.g., handoff algorithms), numerous RF performance tests are typically necessary. In other words, each time a system parameter is changed, a new test must be performed by using the mobile diagnostic to collect a new field test data file. Such repeated field testing is time-consuming. Furthermore, the RF conditions in the cellular network are constantly changing, and thus the reliability of repeated tests under changing field conditions is low.
The present invention relates to an apparatus and a method for recreating RF conditions of a cellular network from previously generated field test data. Cell sectors in a lab setting are connected to a computer-controlled, multi-channel attenuator device which, based on variable control values extracted from the field test data, creates a variable RF loss along a plurality of forward (cell sector to mobile) and reverse (mobile to cell sector) attenuation paths. Such variable control values represent the RF loss which occurred between the network cell sectors and the mobile diagnostic device.
Using a limited number of cell sectors and the multi-channel attenuator, the present invention recreates the network environment represented by the field test data so that a mobile phone connected to the multi-channel attenuator sees essentially the same carrier and interference levels that were observed by the mobile diagnostic device in the field. Thus, the present invention allows RF effects to be observed which were previously seen only in complex deployed cellular networks. Furthermore, since the test conditions remain exactly the same, network parameters can be tested independently of uncontrollable and dynamic parameters that are inevitable when repeated field tests are performed.